© NASA/Ricardo Nunes

Venus at dichotomy

Dominic Ford, Editor
From the Inner Planets feed

Please wait
Loading 0/4
Click and drag to rotate
Mouse wheel to zoom in/out
Touch with mouse to dismiss
The sky at

Venus will be well placed for observation in the evening sky, shining brightly at mag -4.3.

From Ashburn, it will be difficult to observe as it will appear no higher than 16° above the horizon. It will become visible at around 20:20 (EST) as the dusk sky fades, 16° above your western horizon. It will then sink towards the horizon, setting 1 hour and 48 minutes after the Sun at 21:49.

Begin typing the name of a town near to you, and then select the town from the list of options which appear below.

Venus's orbit lies closer to the Sun than the Earth's, meaning that it always appears close to the Sun and is very difficult to observe most of the time.

It is observable only for a few weeks each time it reaches greatest separation from the Sun – moments referred to as greatest elongation.

On these occasions, however, Venus is so bright and conspicuous that it becomes the third brightest object in the sky after the Sun and Moon. It is often called the morning or evening star.

Venus's phase

Venus's phase varies depending on its position relative to the Earth. When it passes between the Earth and Sun, for example, the side that is turned towards the Earth is entirely unilluminated, like a new moon.

Conversely, when it lies opposite to the Earth in its orbit, passing almost behind the Sun, it appears fully illuminated, like a full moon. However, at this time it is also at its most distant from the Earth, so it is actually fainter than at other times.

Venus shows an intermediate half phase – called dichotomy – at roughly the same moment that it appears furthest from the Sun, at greatest elongation. The exact times of the two events may differ by a few hours, only because Venus's orbit is not quite perfectly aligned with the ecliptic.

Venus in coming weeks

The key moments in this apparition of Venus are as follows:

15 Aug 2018 01:09 EDT – Venus at dichotomy
17 Aug 2018 03:58 EDT – Venus at greatest elongation east
25 Sep 2018 00:17 EDT – Venus at greatest brightness
26 Oct 2018 10:11 EDT – Venus at inferior solar conjunction

Over coming weeks, the distance between Venus and the Sun will decrease each night as it sinks back into the Sun's glare. The table below lists how long Venus will remain up after sunset each night; all times are given in Ashburn local time.

Date Sun
sets at
sets at
Altitude of Venus
at sunset
Direction of Venus
at sunset
08 Aug 201820:1022:0420°west
15 Aug 201820:0121:5020°south-west
22 Aug 201819:5221:3518°south-west
29 Aug 201819:4221:1917°south-west
05 Sep 201819:3121:0115°south-west
12 Sep 201819:2020:4313°south-west
19 Sep 201819:0920:2211°south-west
26 Sep 201818:5719:58south-west
03 Oct 201818:4619:31south-west
10 Oct 201818:3519:00south-west
17 Oct 201818:2518:27south-west

A graph of the phase of Venus is available here.

Venus's position

The coordinates of Venus when it reaches dichotomy will be:

Object Right Ascension Declination Constellation Angular Size
Venus 12h27m10s -04°20' Virgo 23.7"
Sun 09h37m +14°08' Leo 31'34"

The coordinates above are given in J2000.0.

The sky on 15 August 2018
Twilight ends
Twilight begins

4-day old moon
Waxing Crescent


4 days old

Rise Culm. Set
Mercury 05:38 12:27 19:16
Venus 10:14 16:02 21:50
Moon 11:16 17:05 22:55
Mars 19:15 23:43 04:15
Jupiter 13:12 18:24 23:35
Saturn 16:59 21:43 02:32
All times shown in EDT.


The circumstances of this event were computed using the DE405 planetary ephemeris published by the Jet Propulsion Laboratory (JPL).

This event was automatically generated by searching the ephemeris for planetary alignments which are of interest to amateur astronomers, and the text above was generated based on an estimate of your location.

Related news

03 Jun 2017, 01:58 EDT  –  Venus at greatest elongation west
17 Aug 2018, 03:58 EDT  –  Venus at greatest elongation east
06 Jan 2019, 01:02 EST  –  Venus at greatest elongation west
24 Mar 2020, 03:31 EDT  –  Venus at greatest elongation east

Image credit

© NASA/Ricardo Nunes




Color scheme